REMEDIATION Spring 2007 Pilot-Scale Evaluation Using Bioaugmentation to Enhance PCE Dissolution at Dover AFB National Test Site Carmen A. Lebr´ on Timothy McHale Robroy Young Dale Williams Matthew G. Bogaart David W. Major Michaye L. McMaster Ian Tasker Naji Akladiss An Interstate Technology and Regulatory Council (ITRC) forum was recently held that focused on six case studies in which bioremediation of dense nonaqueous-phase liquids (DNAPLs) was performed; the objective was to demonstrate that there is credible evidence for bioremediation as a viable envi- ronmental remediation technology. The first two case studies from the forum have been previously published; this third case study involves a pilot-scale demonstration that investigated the effects of biological activity on enhancing dissolution of an emplaced tetrachloroethene (PCE) DNAPL source. It used a controlled-release test cell with PCE as the primary DNAPL in a porous media groundwater system. Both laboratory tests and a field-scale pilot test demonstrated that bioaug- mentation can stimulate complete dechlorination to a nontoxic end product and that the mass flux from a source zone increases when biological dehalorespiration activity is enhanced through nutrient (electron donor) addition and bioaugmentation. All project goals were met. Important achievements include demonstrating the ability to degrade a PCE DNAPL source to ethene and obtaining significant information on the impacts to the microbial populations and corresponding isotope enrichments during biodegradation of a source area. O c 2007 Wiley Periodicals, Inc. INTRODUCTION This is the third in a series of articles on discussions held at an Interstate Technology and Regulatory Council (ITRC) forum that focused on case study projects in which bioremediation of dense nonaqueous-phase liquids (DNAPLs) was performed. The ITRC’s Bioremediation of DNAPLs (BioDNAPL) Team hosted the forum in Long Beach, California, on March 28 and 29, 2006. The ITRC is a coalition of 46 states and the District of Columbia that works with federal agencies (primarily the U.S. Department of Energy [DOE], the U.S. Department of Defense [DOD], and the U.S. Environmental Protection Agency [US EPA]), industry, and other stakeholders to achieve regulatory acceptance of environmental technologies. The BioDNAPL Team, one of 15 ITRC technical teams, aims to develop the technical and regulatory requirements for the bioremediation of DNAPLs, with an emphasis on DNAPLs associated with chlorinated ethenes. The Long Beach Case Studies Forum is part of the BioDNAPL Team’s approach of using case studies c  2007 Wiley Periodicals, Inc. Published online in Wiley Interscience (www.interscience.wiley.com). DOI: 10.1002/rem.20121 5